Vitamin D for asthma protection: what is the optimal timing?

High-dose prenatal and postnatal vitamin D intake appeared to be linked to a reduction of the occurrence of asthma or recurrent wheezing at 3 years of age, results from the VDAART study showed. Furthermore, those with sufficient prenatal and postnatal vitamin D intake were less likely to suffer from atopic asthma at the age of 6.

“Studies have demonstrated that high dietary intake of vitamin D during pregnancy is associated with a reduced risk for asthma or recurrent wheezing in young children,” said Dr Lourdes Ramirez (Brigham and Women’s hospital, MA, USA) [1,2]. “The effects of postnatal vitamin D intake on asthma protection are however less clear.” Dr Ramirez and her colleagues aimed to answer the following questions:

• What is the optimal timing for vitamin D supplementation with regard to asthma protection?
• Do prenatal and/or postnatal vitamin D intake have a different influence on the occurrence of asthma?

The randomised Vitamin D Antenatal Asthma Reduction (VDAART) trial included 881 pregnant women at high risk for offspring asthma [2]. The primary outcome of asthma or recurrent wheezing at 3 years of age was compared between 4 exposure groups:

• High prenatal (4,400 IU per day) and postnatal (≥400 IU per day at the age of 12 months) vitamin D supplementation
• Low prenatal (400 IU per day) and postnatal (<400 IU per day) intake
• High prenatal and low postnatal intake
• Low prenatal and high postnatal intake

Infants that had received a sufficient intake of vitamin D, both prenatal and postnatal, had a numerically reduced risk of recurrent wheezing or asthma at age 3 compared with those who did not receive sufficient vitamin D intake, either prenatal or postnatal, but this result did not reach statistical significance (aOR 0.51; 95% CI 0.24–1.08; P=0.08). Infants in the ‘both’ group had numerically improved odds ratios compared with those in the prenatal only (aOR 0.73; 95% CI 0.35–1.52) or postnatal only (aOR 1.04; 95% CI 0.50–2.15) group. In addition, atopic asthma at age 6, a secondary outcome measure, occurred less frequently in infants that received sufficient prenatal and postnatal vitamin D supplementation compared with those who did not (aOR 0.23; 95% CI 0.06–0.80; P=0.03).

According to Dr Ramirez, these results give some insight into the optimal timing of vitamin D supplementation with respect to asthma protection.

1. Wolsk HM, et al. PLoS One. 2017;12(10):e0186657.
2. Ramirez LG, et al. Association of prenatal maternal and infant vitamin D supplementation with offspring asthma outcomes. Session A13, ATS International Conference 2023, 19–24 May, Washington DC, USA.

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Posted on 25 May, 2023